JPH0148962B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention mainly relates to a shape measuring device for a disc body.

[Technical background of the invention and its problems]

In the case of non-contact detection of minute heights appearing on the surface of a disk, one possible conventional technique is a measuring device that uses interferometry to display an interference pattern on an ITV monitor image. However, if a wide screen is captured on ITV at once, the resolution is limited, making it impossible to detect minute defects. Furthermore, automatic inspection requires an ultra-high-speed image processing function, which is impractical. In addition, when performing interferometry without using image processing, the laser beam, which is coherent light, is divided into two, one beam is irradiated onto a reference mirror, and the other beam is irradiated while rotating the disc. The light is irradiated while moving in the radial direction, and the reflected light from the disc body is caused to interfere with the reflected light from the reference mirror. However, in this case, if the detection point on the surface of the disk body is far from the position of the reference mirror, the optical path difference will change unstablely due to external vibrations, vibrations from the rotation mechanism that rotates the disk body, and other factors. However, there was a drawback that measurements with high S/N ratio could not be performed. Furthermore, when the disc body moves up and down as it rotates, the two optical paths become misaligned, resulting in the loss of interference fringes.

[Purpose of the invention]

The present invention was made in view of the above-mentioned circumstances, and an object of the present invention is to provide an apparatus that performs measurement without affecting measurement accuracy even when relative fluctuations occur between the object to be measured and the measuring light that illuminates the object.

[Summary of the Invention] The present invention allows coherent light emitted from one light source to enter and split into two parallel beams, and
An optical system that focuses both light beams at different positions and irradiates the rotated object while moving it in the radial direction, and deflects the two reflected beams from this irradiation as interference light in a direction different from the direction of incidence. The configuration is such that the shape and position of minute heights or depths that become defects are detected by arranging them and calculating the interference light.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to FIGS. 1 to 4. That is, the configuration of this embodiment includes a light projecting section, an optical system that converts the coherent light from the light projecting section into two parallel light beams, an irradiation optical system that irradiates the two light beams onto the object to be measured, and the object to be measured. A mechanism for rotating the irradiation object,
A drive mechanism that moves the irradiation optical system in the radial direction of the object to be measured, a detection section for interference light due to reflected light from the object to be measured, and a processing section that calculates and displays the signal from the detection section and the position signal with respect to the object to be measured. It is made up of That is, it has a laser oscillator 1 that emits, for example, a He-He laser beam, and a Kester prism 2 is provided on the optical path of the laser beam L emitted from the laser oscillator 1. Two parallel light beams L ₁ , L ₂ deflected by Kester prism 2
An optical system 3 is provided at a position where the light is incident, which is movable in the optical axis direction (X direction) at the light speeds L ₁ and L ₂ by a moving mechanism (not shown). This optical system 3 has a lens barrel 3a, in which a reflecting mirror 4 that reflects the light beams L ₁ and L ₂ downward and focuses the light beams L ₁ and L ₂ reflected at right angles thereto. It has a configuration in which a condensing lens 5 is provided. The condensing lens 5 can freely move toward and away from the reflecting mirror 4. A video disc 6 (hereinafter abbreviated as "disk"), which is an object to be measured, faces the condensing lens 5, and a drive mechanism 7 for holding and rotating the disc 6 is provided. This drive mechanism 7 is equipped with an encoder 8 that detects the rotation angle θ. On the other hand, the reflected beams L ₃ and L ₄ from the disk 6 of the light beams L ₁ and L ₂ irradiated onto the disk 6 pass through the condensing lens 5 and the reflecting mirror 4.
Furthermore, the light is emitted after returning to the Kester prism 2, and a light receiving element 10 is provided via a pinball 9 in order to detect the emitted reflected light L ₃ and L ₄ and convert it into an electric signal. There is. The output signal of the light receiving element 10 enters an amplifier 11, and the amplified signal is processed by an arithmetic processing section 12, and the result is displayed on a display section 13.
Note that the arithmetic processing unit 12 is always inputted with a signal Δθ during rotation of the encoder 8 and a moving distance signal Δx in the moving mechanism of the optical system 3.

Next, the operation of the above device will be explained.

The measurement is started by rotating the disk 6 and emitting the laser beam L to irradiate the disk 6 with light beams L ₁ and L ₂ . That is, the light beams L ₁ and L ₂ project two spots A and B at a distance D on the upper surface of the disk 6, and one of these spots serves as a reference point and the other serves as an observation point. Therefore, for example, as shown in FIG.
When there is a convex defect 14 on the surface, the spot A on the flat part is used as a reference point, and the reflected light L ₃ and spot B on the defect 13 are used as observation points, and the reflected light L ₄ is the height of the defect 14. The interference light is emitted from the Kester prism 2 and received as interference light according to the intensity of the interference light.
Since the light reception signal at this time is different from the light reception signal at a flat portion that cannot be recognized as a defect, it is processed by the arithmetic processing unit 12, and at the same time, each signal from the encoder 8 and the moving mechanism of the optical system 3 is processed. ,
The extent of the shape of the defect 14 (displayed in height) is displayed together with the coordinate position of the disk 6.

Note that by adjusting the vertical movement of the condenser lens 5, the distance D between the spots A and B can be arbitrarily changed, increasing the degree of freedom in measurement. Furthermore, instead of the Kester prism 2, it is free to provide another optical system that deflects the two parallel light beams and causes them to interfere.

〔Effect of the invention〕

Since both the reference point and the observation point are placed on the object to be measured, it is resistant to vibration and external noise, and it is possible to obtain an interference signal with a high S/N ratio without being affected by the vertical movement of the object to be measured. Highly accurate measurements can be performed.

[Brief explanation of drawings]

FIG. 1 is a plan view showing one embodiment of the present invention, and FIG.
The figure is a perspective view showing the main part of the above embodiment, FIG. 3 is a diagram showing the transmission of light in a Keplerian prism, and FIG.
The figure is a cross-sectional view showing an example of measurement. DESCRIPTION OF SYMBOLS 1... Laser oscillator, 2... Kester prism, 3... Optical system, 7... Drive mechanism, 8... Encoder, 9... Collimator, 10... Light receiving element,
12... Arithmetic processing unit, 13... Display unit.

Claims (1)

[Claims] 1. A projector that projects coherent light, a splitting optical system that splits the coherent light into two beams, and focuses and irradiates the two beams onto different positions on the surface of the object to be measured. a condensing optical system, a photoelectric conversion element that receives reflected light from the object to be measured and interfered within the splitting optical system, and a rotation mechanism that rotates the object to be measured;
A rotation angle detector outputs a rotation angle signal during rotation of the object to be measured, and a movement distance signal for relatively moving the object to be measured and the laser beam that irradiates it in the radial direction of the object to be measured. a moving mechanism for outputting;
a calculation unit that inputs the output signal from the photoelectric conversion element, the rotation angle signal, and the movement distance signal in the movement mechanism to calculate and process a minute height on the surface of the object to be measured and its position; 1. A shape measuring device comprising: a display section that displays a processed signal from the section numerically or graphically. 2. The shape measuring device according to claim 1, wherein the dividing optical system comprises a Kester prism. 3. A patent characterized in that the moving mechanism consists of a moving optical system that is made up of a reflecting mirror and a condensing optical system that focuses the laser beam reflected by the reflecting mirror, and is movable in the radial direction of the object to be measured. A shape measuring device according to claim 1.